Citing a person familiar with the matter, the financial publication said the SEC wants to make sure investors weren't misled. The probe isn't an indication that investigators have seen any evidence of misconduct.

"The good news flipped by the bad news makes one wonder what Apple knew," said James Cox, a law professor at Duke University quoted in the report. "It's not surprising for the SEC to come in and look afterward, given the pressure and publicity regarding their handling of a lot of cases," he said, referring to Bernard Madoff's alleged $50 billion Ponzi scheme.

Spokespeople for both Apple and the SEC declined to comment.

An SEC lawyer who teaches at Wayne State Law School said securities regulators would be hard pressed to build a case against the Cupertino-based company.

"It would be difficult, and certainly a new area of the law," said Peter Henning. "You would have to pin down exactly what they knew, and with a health issue —unlike a merger or a decline in revenue —it's not subject to definitive answers."

On January 5 Jobs disclosed that a hormone imbalance was causing him to lose weight but that he was undergoing treatment and planned to remaining as chief executive. Shares rose 4.2 percent. But just nine days later, the Apple co-founder spooked industry watchers with his decision to take medical leave through June, saying his health problems turned out to be "more complex" than he thought. Apple shares have since fallen 8.4 percent.

A corporate governance expert at Chadbourne & Parke told Bloomberg that Apple's board may have met its obligation to shareholders by announcing Jobs would be on leave.

"It's really an issue of the ability of the CEO during the period of his ill health to continue to advise and consult and manage the affairs of the company," said Edward Smith, who said the board isn't obligated to give specific details about Jobs' illness. "Someone might be able to [consult] from a hospital bed for several weeks just as well as they may do it from the office."

It's been speculated that Apple will inevitably face lawsuits from shareholders unhappy with the company's recent secrecy over Jobs uncertain health. Such suits would be the first of their kind and represent uncharted territory for the US legal system.

Bloomberg on Friday cited "people who are monitoring [Jobs'] illness" as saying he is considering a liver transplant as a result of complications that followed his pancreatic cancer treatment in 2004.